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[英]How to serve a file in ASP.NET Core while it's still being written
[英]Asp.Net Core: how to make the browser show file as being downloaded before it's sent
我有以下生成文件的操作:
public async Task<IActionResult> GetFile()
{
//some long running action to actually generate the content
//(e.g. getting data from DB for reporting)
await Task.Delay(10000);
return File(new byte[]{}, "application/octet-stream");
}
問題是當用戶關注該鏈接時,在點擊操作和顯示文件的瀏覽器之間存在長時間的延遲。
我真正想要的是,ASP.Net發送帶文件名的頭文件(因此瀏覽器會向用戶顯示文件已開始下載)並在生成文件內容時延遲發送Body。 是否有可能做到這一點?
我嘗試了以下方法:
public async Task GetFile()
{
HttpResponse response = this.HttpContext.Response;
response.ContentType = "application/octet-stream";
response.Headers["Content-Disposition"] = "inline; filename=\"Report.txt\"";
//without writing the first 8 bytes
//Chrome doesn't display the file as being downloaded
//(or ASP.Net doesn't actually send the headers).
//The problem is, I don't know the first 8 bytes of the file :)
await response.WriteAsync(string.Concat(Enumerable.Repeat("1", 8)));
await response.Body.FlushAsync();
await Task.Delay(10000);
await response.WriteAsync("1234567890");
}
上面的代碼工作,如果我沒有response.WriteAsync
,我會很高興response.WriteAsync
前8個字節用於發送標頭。
還有其他方法可以克服它嗎?
實際上,有問題的代碼可以正常工作。 問題是, 在發送8個字節之前 , Chrome不會將文件顯示為已下載
但是,如果你想寫類似的東西,可以考慮閱讀Stephen Cleary的一些有用的抽象。
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